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Several representatives of this family of small, diurnal frogs are famous for their bright skin coloration and associated toxins. There are from four to seven genera in this family, and less than 200 species. Distribution is restricted to humid tropical America, from Nicaragua to Brazil, with the greatest diversity in northwestern South America.

Dendrobatids are the most brightly colored of any anuran group. Although the large genus Colostethus is drab-colored and non-toxic, the derived "aposematically colored dendrobatids" (members of the genera Dendrobates, Phyllobates, and their kin) have skin toxins comprised of lipophilic alkaloids, some of which can easily kill a human if ingested. The only other anuran group exhibiting both bright colors and lipophilic alkaloids are the unrelated Mantellas (Rhacophoridae). Dendrobatids are small (20-40 mm snout-vent length, though the putative basal species, the nocturnal Aromobates, attains lengths of 62 mm). Synapomorphies of this family include the presence of a retroarticular process of the mandible, and the arrangement of the superficial slip of the m. depressor mandibulae. Additional possible synapomorphies include the tendon of the semitendinosus piercing the m. gracilis major and m. gracilis minor, divided dermal scutes on the dorsal surfaces of fingers, cephalic amplexus (amplexus is entirely lacking in some species), and the transport of aquatic larvae on the dorsum of the parent.

Almost all dendrobatids are diurnal. Most are terrestrial; some are arboreal. The common name, dart-poison frogs, is derived from a practice of the Indians of the Ember Choco in Colombia, in which they rub their blowgun darts onto the backs of Phyllobates terribilis to load the darts with poison (Myers et al., 1978). Dendrobatids are ant and mite specialists, and some researchers have argued that their skin toxins are derived from precursor molecules in the ants they eat (e.g. Caldwell 1996). The combination of aposematic coloration and diurnal habit has allowed members of most dendrobatid species to clump in space, largely freed from the risks of predation. Complex forms of sociality, territoriality, courtship, and parental care have evolved in many of these species. In all species for which there is data, tadpoles are carried on the back of the adult (sometimes the male, sometimes the female), usually from a terrestrial oviposition site to water. In several species of Dendrobates, the female carries tadpoles individually to the water-filled axils of bromeliads or treeholes, depositing a single tadpole into each crevice visited. The mother later returns, repeatedly, to each of her tadpoles, which have reduced beaks and denticles, and deposits unfertilized eggs for them to eat. Several species of dendrobatids are popular in the pet trade.

Dendrobatids are neobatrachians, but relationships among the families of these "advanced" frogs are almost wholly unresolved. Within the Neobatrachia, dendrobatids have sometimes been placed in the Ranoidea, and sometimes in the Bufonoidea. Ambiguity at this level of history points to the utter confusion that has supplanted all attempts to make sense of dendrobatid evolution. Current hypotheses of relationship include dendrobatids and petropedetine ranids as sister taxa, dendrobatids and arthroleptids, and dendrobatids and hylodine leptodactylids. Other authors have simply placed Dendrobatidae within the Ranoidea, in part due to several characters they have that are plesiomorphic to Ranoidea (e.g. cartilaginous sternum, horizontal pupil, unnotched tongue). The dendrobatids are probably monophyletic. Within Dendrobatidae, Aromobates is usually considered basal. Finally, some genera currently in use have not undergone rigorous phylogenetic analysis (Minyobates and Epipedobates, members of which previously belonged to Dendrobates), and it is questionable if they will persist.

There are no known dendrobatid fossils.

Caldwell, J. P. 1996. The evolution of myrmecophagy and its correlates in poison frogs (Family Dendrobatidae). Journal of Zoology 240:75-101.

Ford, L.S. 1990. The Phylogenetic Position of Poison-dart Frogs (Dendrobatidae): Reassesment of the Neobatrachian Phylogeny with Commentary on Complex Character Systems. Ph.D. Dissertation, The University of Kansas, Lawrence, Kansas.

Contributors

Heather Heying (author).

Glossary

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

metamorphosis

A large change in the shape or structure of an animal that happens as the animal grows. In insects, "incomplete metamorphosis" is when young animals are similar to adults and change gradually into the adult form, and "complete metamorphosis" is when there is a profound change between larval and adult forms. Butterflies have complete metamorphosis, grasshoppers have incomplete metamorphosis.

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This material is based upon work supported by the
National Science Foundation
Grants DRL 0089283, DRL 0628151, DUE 0633095, DRL 0918590, and DUE 1122742. Additional support has come from the Marisla Foundation, UM College of Literature, Science, and the Arts, Museum of Zoology, and Information and Technology Services.